Two-way projection system for data input

ABSTRACT

A data input terminal comprising a two-way projection system for the selection of desired input messages from a library of selectable messages. The library of messages is optically displayed in groups on a projection screen and selection of desired messages from the projected group is optically detected to provide electrical output signals representing screen locations corresponding to the selected messages.

United st ates Pat ent/t 11 1 T Worthington, 'Jr, et all;

5111 3,325,730 {451 July 23,1974

I 4] TWO-WAY PROJECTION SYSTEM FOR 7 DATA INPUT Y [75] Inventors: HarveyR. Worthington, .lr.,

Concord; Edward B. Rawson, Lincoln; Daniel B. Schwarzkopf, V Stow, allof Mass. [73] Assignee: Searle Mediclata, lnc., Waltham, I Mass. I [22]Filed: Nov. 7, 1972 21 Appl. No.: 304,554

[52] US. Cl...:. 235/92 V, 235/92 R, 250/219 D,

. 340/324 R [51] Int. Cl. G06m 11/00 [581 Field of Search, 235/92 .V;340/324 R; ,r y I I r I 250/219 Dj- [56] y References Cited UNITEDSTATES PATENTS, 3,534,359 I'D/1970 -Harris 340/324 RPrirrzkzry-Examiner-Paul J. Henon 1 Assistant Examiner loseph M. Thesz,Jr.

Attorney, Agent, or FirmWeingarten, Maxham &

Schurgin 57 ABSTRACT A data input terminal comprising a two-wzty projec-I tion system for the selection of desired input messages from a libraryof selectable messages. The library of 7 messages is optically displayedin groups on a projection screen and selection of desired messages fromthe projected group is optically detected to provide electrical outputsignals representingscreenlocationscorresponding to the selectedmessages. 3

' 14 Claims,6' Drawing Figures VERIFICATION COUNTER SELECTOR 28 SWITCHESADDRESS STORAGE NEW "*C" AR CHAR CHAR- SELECTION CLEAR UTILIZATION(DELAY) PATENTEB JUL 2 3 I974 SLIDE SHEEI 10F '2 SELECTOR SWITCHES ADF66 HQLD--- I DATA-M cHAR ADR HOLD- 68 FIG. 1

I 5 2 70 HOLD L CLEAR UTILIZATION SELECTION (DELAY) PATENTEB L SHEU 2 BF2 4 FIG. 2

ELECTRONICS HILIIIIIIII LOAD COUNTER o oooooo MULTIPLEXER FIG. 5

HOLD

Two-WAY PROJECTION SYSTEM FOR DA TA INPUT s FIELD or THE INVENTION vThis invention relates to data input terminals and in particular toterminals for the optical selection of input data from a library ofinformation.

BACKGROUND OF THE INVENTION With digital information handling systemsbecoming more commonly used in all fields, increasing demand is beingexpressed for the provision of effi'cient data input terminals whichpermit the selection of input data from a large libraryof availableinputs. In such applications it is necessary to both display for theoperators selection the information from which he is permitted to selectpredetermined input messages and also to permit simple and foolproofcommunication to the input terminal of the operators data selection. i

In the rapidly expanding field of medical datasysterns, instances exist.for which'it is desirable to provide multiple data input terminalshavingat low cost, flexibilities and capacities not previously availableinfthe prior art-systems. In one such application, information handlingsystems are provided in hospitals to process the flow of medical andadministrative information. In such cases it is necessary to provide aplurality of information input terminals whereby, for example,individual nursing stations can call up orders or services forindividual patients and select them from a vast body of possible medicalrequests. a

. Exemplary priorsystems which employ a switch matrix and overlay systemhave been found satisfactory for many applications but are limited inthe size of the' input data library and often use mechanical switches toenable selection-of input data. Prior systems which luse a projection ofselectable input data without switches for data selection requirecomplex and expensive scanning systems to enable electro-opticalseparation of-different portions of the projected image for identifyingthe image area corresponding to selected data. One prior art attempt toprovide this capability is shown in Harris, U.S. Pat. No. 3,534,359.

vast library of available input data is provided accordsing to'thepresent invention in an input terminal foruse.

with a medical information handling system. The information inputterminal employs a fully optical datadisplay and selection system whichpermits rapid accessto,

and selection from the whole input data' library. The fully opticaldesign is economical in the use of display area to increasethe possiblelibrary size and provides for input data selection without the use ofcostly me system onto a photodetector array with predetermined alignmentbetween screen image locationsand detec-.

tors in the Iarraybut at an 7 to activate any detector in thearrayr'when the-operation of the system of FIG. 1;

2 optical intensity insufficient tor wishes to make a data inputselection a light source is applied to the screen at a locationcorresponding to the selected data to cause an intense spot of light tobe focused onto the detector array activating a corresponding detector.The detector array is scanned to tie termine the activated detector anda digital signal is generated to represent the activated detector. Thearray scanning and activated detector determination are made withprovisions to reject spurious activations.

An additional,digital signal is generated to indicate which transparencyis displayed and together, the two digital signals completely specifyselected input information from a very large number of possible choices.The use of projectable transparencies for each repertory furtherfacilitates modifications to the library of selectable inputs by simplereplacement of one or more transparencies.

BRIEF DESCRIPTION or THE DRAWINGS These and other features-of thepresent invention will be more fully understoodby reference to thedetailed description of preferred embodiments presented below forpurposes of illustration, and not by way of limita tion, and to theaccompanying drawings of which:

FIG. 1 is a pictorial and schematic diagram of a twoway projectionsystem according to the invention;

FIG. 1A is a view of a typical information repertory projected by thesystem of FIG. 1:;

FIG. 2 is a diagrammatic view of the projection porscreen reflectivepointer for FIG. 3 is a diagram of a modified projection for use in theinvention with a data selection;

FIG. 4 presents a modification of the projection sys- 1 tem andreflective pointer for use in the invention; and

The feature of rapid selection of input data from a FIG. 5 isa pictorialand schematic diagramof a modified detector tion. v

DETAILED DESCRIPTION or A PREFERRED EMBODIMENT I To provide-a flexible,easy to use, and low cost input terminalfor selection of multiple choiceinput data a two-way projection system is shown in FIG. 1. Thecomponentsindicated could typically be contained within a small console but areshown without reference to the console in FIG. 1 for clarity ofunderstanding. In a rear projection system, a projection screen 12 ispositioned to receivelight directed from a-projector 14 at a focal planeof the projected light. Light eminating fromthe rear projection surfaceof the screen 12 is focused by a lens system .16 onto the plane of anarray of photodetectors 18. v

Theprojector- 14 may typically be any of the several available,externally programmable random access projectors such as, for example,the Kodak Carousel RA- 950 or RA-960 projector. The projector 14 has amagazine or tray 20 from which 80, or slides may be selected forprojection in'response to externally applied control signals to bedescribed below.

A typical slide repertory is indicated in FIG. 1A wherein an image 22 isshown to contain a plurality of selectable input messages 24 associatedwith selection points 26. The repertory of slide 22 might find typicaland imaging system for use in the inven- 3 application in ahospitalinput terminal where it may be desired to provide to the hospital datasystem selected pharmacy or test orders pertinent to a particularpatient@ This selection is made directly from a projected list ofpossible pharmacy or service instructions presented in the format 22. itis to be noted that more or less messages may be provided in the samerepertory.

A selector switch system 28 is provided adjacent to the projectionscreen 12 for example when mounted in a console to enable the terminaloperator to manually select which of the 80 or 140 slides is desired fordis play and accordingly for selection of particular informationcontained thereon. The output of the switch operates through theprojector 14 to cause the magazine to be appropriately positioned fordisplaying that slide.

Selection of desired information from a displayed image 22 is achievedby illuminating a point 26 with the light spot from a small light sourcesuch as pen light 30.. The projection screen 12 will normally be of atranslucent material which is sufficiently lightdispersive to provide aclear image of slides projected by projector 14 onto screen 12 and alsosufficiently transmissive of light to transmit significant portions ofillumination provided by the pen light 30 from the operators side ofscreen 12 to the reverse side facing the projector 14 and lens system16. The pen light 30 and screen 12 are adapted to provide radiation oflight from the back of screen 12 toward the'lens system 16 in a quantitysubstantially greater than diffused illumination from the projector 14or from ambient room light. This may be facilitatedby not subjecting thepoints 26 to illumination from the projector and by employing a size forpoint 26 which corresponds to the detector size.

Typically the array 18 will contain a matrix of photosensitivetransistors 32. The lens system 16 and array 18 are placed adjacent tothe projector. 314 but slightly off axis from each other due to physicalplacement requirements. The photosensitive detector array 18 ispositioned with the lens system 16 so that light from each selectionpoint 26 is imaged onto a corresponding photosensitive transistor 32.The number of selection spots 26 which canbe .placed on a single slidewill be generally limited by the abilities of the individual projector14 to consistently position the projected'irnage.

As indicated in FIG. 1', the collectors of all transistors 32 in asingle row are tied together and biased through a single resistor 34.All resistors 34 are supplied from a Single voltage source 36.Electrical connections are fed from each row at the point of junctionwith the collectors of transistors 32 to row output terminals of thearray 18 which are in turn connected to a sampling, multiplexer circuit38. Multiplexer circuit 38 provides at its output, each of the outputsignals specified by digital signals from a counter 40.

The emitters of all phototransistors 32 in a column are joined togetherand electrically connected externally of array 18 to a decoder circuit42 which sequentially grounds the emitters a column at a time inresponse to a control input from counter 4h. The counter 40 continuouslycycles through a predetermined count in response to clocking signalsfrom an oscillator 44. Typically most significant bits from the counter40 correspond to column addresses and are applied as the control signalto the decoder circuit 42 which, for each binary state in the mostsignificant bits, grounds a corresponding column of emitters from thearray 18. The least significant bits from the counter 40 are applied tothe sampling circuit 38 to connect to a DATA output line 46 acorresponding one of its row inputs depending upon the binary state ofthe least significant bits.

The total binary count of the counter 40 is applied to an addressstorage register 48. The register 48 is caused to respond to and storethe digital contents of the counter) by a LOAD input from an AND circuit50. The AND circuit 50 receives the output of the multiplexer circuit 38as well as a NOT HOLD input signal on a line 52. The NOT HOLD signalwill he subsequently described, but generally indicates a systempreparedness to accept new information. When both signals occur, thecounter 4D is at a binary count which connects signals at the decoder 42and sampler 38 to the row and column of an illuminated photosensitivetransistor. The register 48 is loaded with the digital contents of thecounter 40 at that time, this digital signal indicating whichphotodetector is illuminated. A comparator 54responds to the stored datain register 48 and the output of the counter 40 to provide an addressoutput on a line 56 (ADR) in response to digital equality between itstwo inputs. As is apparent, circuit 54, according to conventionaldigital clocking techniques, will make its comparison of the previouslystored counter signal with the about to be stored counter signal.

Toprovide a verification of the illumination of a photosensitivetransistor 32 a verification counter 58 is provided to cause severalsequential rapid samplings of thesamephotosensitive transistor 32 beforeacceptance of that indication as a valid input of data. To accomplishthis an AND gate 60 receives the ADR signal from the line 56 and theDATA output on line 46 of multiplexer circuit 38 as well as the NOT HOLDsignal on line 52 and a NOT CHAR signal to be explained.

(Coincidence of all four signals causes application of a signal to thecount-up input of counter 58 causing it to advance one digital count. Afurther AND gate 62 receives theADR address output the HOLD signal, aNOT DATA signal derived from line 52 and the NOT CHAR signal.Coincidence of all signals causes the counter 58 to countdown a digitalstep in response to a signal applied to its count-down input from thegate 62; The counter 58 is preset through an OR gate 64 when either asignal is received from an AND gate 66 of an AND gate 68. The AND gate66 receives a NOT ADR signal derived from the address signal on line 56and the DATA signal on line 46, the NOT HOLD signal and the NOT CHARsignal; The AND gate 68 receives the same last two mentioned signals andADR address signal on line-56 and the NOT DATA signal derived from line46;.

The indicated NOT signals may be-derived from any of the knowntechniques including inverting outputs or inputs, or separate inverters.

It can be seen that the counter 58 is preset through the OR gate 64 ifthe DATA signal from the multiplexer circuit 38 is received at a timewhen the stored address in the register 48 is different from the stateof the counter 40 as indicated by the NOT ADR signal and if the NOT HOLDand NOT CHARconditions exist. Similarly, if an ADR signal is preset withNOT DATAand the NOT HOLD and NOT CHAR signals exist, the counter 58 willbe preset.

available from all slides in the magazine 20.

The counter 70 is causedto count up when boththe ADR and the" DATAsignals arepresent providedthat NOT HOLD and NOTCHAR exist. After asufficient digital count, the counter 58 provides a count-up completesignal to a hold register '70 and a new character register 72. Thiscount-up complete signal will cause the hold register 70, typically abistable memory circuit, to provide the I-IOLD signal on an output 52.This signal is applied as indicated above in the system. At the sametime the new character register 72 responds to the count-upcomplete'signal .74- to produce a new character output signal CHAR online 74 to indicate that the digital number in the register 48represents the message selected for input through the terminal. Thisdigital representation is available atoutput line 76 of register 48.

The CHAR signal-and data on line 76 are applied to a utilization device78 which may be a data processing system fo'r a hospital. Afterreceiving the dataon line 76, the utilization device 78, returns aclearsignal to reset the new character register 72. For purposes ofunderstanding this invention the utilization device 72 may be viewed.asproviding a delayed clear output in response to the CHAR signal toreset the register 72.

I HOLD signal and establishthe NOTHOLD signal. This count-down functionprovides a predetermined delay after theacceptance of information andafter the removal of the light spot as produced by the pen light 30 fromthe surface of the screen 12 to prevent acceptance of thesameiinformation twice unless it is purposely desired. r t

Along withkthe CHAR signal on line 74, a SLIDE KEY signalon line 80.fromthe switches 28 indicating the particular slidedisplayed on the screen12 is ap plied to the utilization device 80. The slide and selectioninputs on lines 76 and80 to the utilization device 78 provide completeinformation on the specific mes sageselected by the operator from thevast; librar Referring now to FIG. 2 a diagrammatic view of the two-wayprojection system is indicated showing the adjacent relationship of theprojection optics with the detector and imaging optics. In-particular alamp 82 is provided to direct light through a condenser system 84 and aslide transparency 86 to a lens system 88. Light from the lens system 88is imaged on a translucent projection surface or screen 90. Theprojection surface90 may be a glass or plastic plate constructed asindicated above to provide the necessary degree of translucence forpresenting an image of the slide as well as transmit ting light from thepen light 30. Preferably, the screen 90 is marked to indicate thelocations of the selection points 26. This may be achieved with anopaque surface coating 92which is perforated with transparent portions94 in areascorresponding to the selection points 26 and has translucentregions 96 in the area of 6 The light frornathe pen light .30 is imagedthrough transparent portions 94 by an optics system 98 onto a projectionfor message selections 24.

photosensitive detector array'100 which is in turn samback illuminationfrom the projector with ahigh specular characteristic and by employingthe qualities of the Fresnel lens to direct it toward the optical system98. and the detector array 100 as shown in FIG. 2. By placing the mirror112' on the plane coatedsurface 108 of the screen 90 proper axialalignment of the mirror 112 is insured; As'isapparent for the FIG. 3embodiment, the slides will be, designed to provide illumination throughpoints 26 to portions 110.

In FIG. 4 a further'modificationis indicated wherein a screen 114 isprovided with a dispersive coating 116 similar to coating 108 andtransparent portions 118 aligned with the points26. A corner reflectorlis provided for placement over the transparent portions 118 to reflectlight from the projector backwards along its'path of incidence. Thecomplete optical system is shown in FIG. 4 to include a beam splittermirror'l22 in the path of illumination from projector 14 to screen 114.Mirror 122 passes'light fromthe projector 14 but reflects light returnedby retroreflector l20through a lens system 124 to a detector array 126for electronic sampling as indicated above. The screen 104 and mirror112 of FIG. 3 may also be used in the FIG. 4 embodiment to replacescreen 1.14 and 'retroreflector120.

zontal row l36. No detector is in both column 134 and row 136. Verticalslit 130 will cause a vertical bar of light to fall on array 138 foreach selection, and that bar will illuminate a detector in row 136corresponding to the column on the displayed repertory containing theselected message. Similarly, horizontal slit 132 causes a horizontal.bar of light which illuminates a detector in column 134correspondingtothe displayed row containing the selectedmessage. I I I Acounter has its most significant bits applied through a multiplexer 142'to sample the state of each of the photodetectors in the horizontal row136. A multiplexer 144 is provided to sample the photodetectors in thecolumn 134 in response to the least significant bits in counter 140. Themultiplexers 142 and 144 detect illumination of a detector in the row136 and column 134 and apply respective signals indicative thereof threeinputv conditions are met. Register 148 is similar toregister 48 of FIG.land stores the digital state of counter 140 The remaining circuitry mayfollow the pattern of FIG. 1. I

In place of slits 130 and 132 in mask 128, discrete holes may beemployed. Additionally, slits which do vnot cross may be employed andmay be made wide to accept cylindrical lenses to increase the intensityof the bars of light.

With the above indicated projection andelectronic detection system it ispossible to provide a library of selectable information for multiplechoice question and answer purposes or selection of input data from avast library of-possible inputs by providing a raster of selectable dataon each of a plurality of transparent images. A particular image and thecorresponding selection from that image are encoded to provide an outputindication of the desired information and to provide verifi-.

cation for each selection. The terminal furthermore provides rapid entryof a vast amount of data with selections from a plurality of differentslides by using a random access projector. Moreover, the problems ofswitch contact bounce are eliminated by using an optical system andmultiple scan verification for responding to the selection of individualdata from each display raster.

The library of selectable input information is easily altered byproviding new transparencies and by changing the recognized informationin the utilization device as for example by altering addressable look-uptables. The selection sequence may be made adaptive as by employingdata-processing to define the repertory to display on the basisof pastselections.

It will occur to those skilled in the art that in addition to thesystemdisclosed above, further modifications and alternatives can bedevised to implement the spirit of the invention and accordingly it isintended to limit the scope of the invention only as indicated in thefollowing claims.

What is claimed is:

1. A two-way projection system for presentation of and selection fromrepertories of selectable information said system comprising:

a projection surface;

means for projecting a repertory of selectable information on saidprojection surface in predetermine alignment; a light reflector forplacement at selected positions on said projection surface to reflectlight provided by said projecting means from the selected positions onsaid projection surface associated with selectable information; and

means responsiveto light from said light reflector emanating byreflection'from said projection surface for detecting the relativeposition of said selected position on said projection surface thereby toprovide an indication of the location on said projected image of saidselected position;

said projection surface including means for providing a visible displayof said selectable information in the projected repertory for viewingand for transmitting a portion of the light projected onto said surfaceand reflected by said light reflector at said selected position forreradiation toward said-detecting means in amagnitude substantiallygreater than other light emanating from said surface.

2. The two-way projection system of claim 1 wherein 6 said detectingmeans further includes:

v an array of photosensitive detectors;

means for imaginglight from 'said selected position onto saidphotosensitive detector array with predeterrnined alignment between eachdetector in the array and predetermined positions of said selectedposition on said projection surface; and

means for sampling thephotosensitive detectors in said array todetermine which of said detectors is receiving illumination from saidlight reflector at a selected position.

3. The two-way system of claim 2 wherein:

said imaging means includes means for producing on said detector array agenerally focused image of said projection surface;

said detector array includes a two dimensional matrix of saidphotosensitive detectors; and

said sampling means includes means for scanning the rows and columns ofsaid matrix of detectors to provide a digital indication of the positionof a detector illuminated by light from said light reflector at saidselected position. p I

4. The two-way projection system of claim 3 wherein said scanning meansfurther includes:

means for providing a plurality of scans of said detector array andcorresponding indications of the position of an illuminated detector;

means for determining that the indicated detector during adjacent scansremains the same for a predetermined number of adjacent scans to providea verified detector indication; and

means responsive to the verified detector indication for providinganoutput representation of the corresponding detector after saidpredetermined number of adjacent scans.

5. The two-way projection system of claim 2 wherein said imaging meansincludes a mask with apertures therethrough in a two dimensionalarrangement providing a pattern of light on said detector arrayin'response to light emanating'from a selected position on saidprojection surface; and said detector array includes a two dimensionalarrangement of detectors positioned for selective illumination by'saidpattern of light. 6. The two-way projection system of claim 1 whereinsaid projecting means further includes:

a projector containing a plurality of selectable informationr'epertories for projection; means for advancing said projector from oneselectable repertory for projection to a different selectable repertoryfor projection; and means for providing an' output indication of therepertory projected from said plurality of selectable reper'tories. I 7.The two-way projection system of claim 1 wherein said projection surfacefurther includes:

a light diffusing coating; and a plurality of apertures through saidlight diffusing coating at predetermined points thereby to more readilytransmit light from said light director for radiation to said detectingmeans when said selected position coincides with one of said apertures.8. The two-way projection system of claim 1 wherein said projectionsurface includes a Fresnel lens.

9. The two-way projection system of claim 1 further including:

abeam-s plitter; in the path of and transmissive to light from saidprojecting means to said projection surface; v I said beam-splitter.responding to light emanating from said projection surface to redirectthe emanating light; and

means for imaging the redirected light on said detecting means. 7 I 10.The two-way projection system of claim 9 wherein said light reflectorincludes a retro-reflector.

11. Atwo-way projection system for an inputtermi nal and providing forthe display of a repertory of sesaidrepertory including a plurality ofinformation selections and selection points projected in alignment withsaid predetermined portions;

light director means for providing a rear emanation of light from saidsurface at one of said predetermined portions;

a two-dimensional array of light sensitive detectors arranged in a rowand column pattern; 4

means for forming on said array a light pattern in responseto lightemanating from said one of said predetermined portions of saidprojection surface, said pattern activating one or more detectors;

a counter cycling through a predetermined total count with each countstate designating a row and column combination;

means responsive to the count cycling of said counter for scanning saidarray of detectors to provide a first signal when the row and columncombination designated by the count state identifies an activateddetector; means for storing the count state corresponding to 10 saidfirst signal; means for comparing the stored count state for a priorfirst signal with the current count state of said counter to provide asecond signal in response to identity in the count states compared;means for counting sequential second signals coincident with said firstsignal toward a predetermined total count; means for reinitiating thecounting of said counting means prior to its predetermined total countin re sponse to one of said first and said second signals without theother; and means responsive to the predetermined total count of saidcounting means for providing an output indication to indicate that thestored count state represents input information. 1 12. The two wayprojection system of claim 11 further including:

means responsive to said output indication, said second signal and theabsence of said first signal for counting toward a further predeterminedtotal count; and means responsive to said further predetermined totalcount for removing said output indication. 13. The two-way projectionsystem of claim 11 wherein:

said projection surface includes translucent portions for forming animage and transparent portions; said projection means includes a randomaccess pro jector for transparencies containing said repertories andmeans for selecting a transparency for proand a single column ofdetectors.

1. A two-way projection system for presentation of and selection fromrepertories of selectable information said system comprising: aprojection surface; means for projecting a repertory of selectableinformation on said projection surface in predetermined alignment; alight reflector for placement at selected positions on said projectionsurface to reflect light provided by said projecting means from theselected positions on said projection surface associated with selectableinformation; and means responsive to light from said light reflectoremanating by reflection from said projection surface for detecting therelative position of said selected position on said projEction surfacethereby to provide an indication of the location on said projected imageof said selected position; said projection surface including means forproviding a visible display of said selectable information in theprojected repertory for viewing and for transmitting a portion of thelight projected onto said surface and reflected by said light reflectorat said selected position for reradiation toward said detecting means ina magnitude substantially greater than other light emanating from saidsurface.
 2. The two-way projection system of claim 1 wherein saiddetecting means further includes: an array of photosensitive detectors;means for imaging light from said selected position onto saidphotosensitive detector array with predetermined alignment between eachdetector in the array and predetermined positions of said selectedposition on said projection surface; and means for sampling thephotosensitive detectors in said array to determine which of saiddetectors is receiving illumination from said light reflector at aselected position.
 3. The two-way system of claim 2 wherein: saidimaging means includes means for producing on said detector array agenerally focused image of said projection surface; said detector arrayincludes a two dimensional matrix of said photosensitive detectors; andsaid sampling means includes means for scanning the rows and columns ofsaid matrix of detectors to provide a digital indication of the positionof a detector illuminated by light from said light reflector at saidselected position.
 4. The two-way projection system of claim 3 whereinsaid scanning means further includes: means for providing a plurality ofscans of said detector array and corresponding indications of theposition of an illuminated detector; means for determining that theindicated detector during adjacent scans remains the same for apredetermined number of adjacent scans to provide a verified detectorindication; and means responsive to the verified detector indication forproviding an output representation of the corresponding detector aftersaid predetermined number of adjacent scans.
 5. The two-way projectionsystem of claim 2 wherein said imaging means includes a mask withapertures therethrough in a two dimensional arrangement providing apattern of light on said detector array in response to light emanatingfrom a selected position on said projection surface; and said detectorarray includes a two dimensional arrangement of detectors positioned forselective illumination by said pattern of light.
 6. The two-wayprojection system of claim 1 wherein said projecting means furtherincludes: a projector containing a plurality of selectable informationrepertories for projection; means for advancing said projector from oneselectable repertory for projection to a different selectable repertoryfor projection; and means for providing an output indication of therepertory projected from said plurality of selectable repertories. 7.The two-way projection system of claim 1 wherein said projection surfacefurther includes: a light diffusing coating; and a plurality ofapertures through said light diffusing coating at predetermined pointsthereby to more readily transmit light from said light director forradiation to said detecting means when said selected position coincideswith one of said apertures.
 8. The two-way projection system of claim 1wherein said projection surface includes a Fresnel lens.
 9. The two-wayprojection system of claim 1 further including: a beam-splitter in thepath of and transmissive to light from said projecting means to saidprojection surface; said beam-splitter responding to light emanatingfrom said projection surface to redirect the emanating light; and meansfor imaging the redirected light on said detecting means.
 10. Thetwo-way projection system of claim 9 wherein said light reflectorincludes A retro-reflector.
 11. A two-way projection system for an inputterminal and providing for the display of a repertory of selectableinput information and for the identification of selected inputinformation, said system comprising: a projection surface formed toinclude a surface which provides a forwardly viewable image of a rearprojected information repertory and to provide substantial transmissionof light from front to rear for backward emanation of said light in atleast a plurality of predetermined portions; means for rear projecting arepertory of selectable information for display on said surface; saidrepertory including a plurality of information selections and selectionpoints projected in alignment with said predetermined portions; lightdirector means for providing a rear emanation of light from said surfaceat one of said predetermined portions; a two-dimensional array of lightsensitive detectors arranged in a row and column pattern; means forforming on said array a light pattern in response to light emanatingfrom said one of said predetermined portions of said projection surface,said pattern activating one or more detectors; a counter cycling througha predetermined total count with each count state designating a row andcolumn combination; means responsive to the count cycling of saidcounter for scanning said array of detectors to provide a first signalwhen the row and column combination designated by the count stateidentifies an activated detector; means for storing the count statecorresponding to said first signal; means for comparing the stored countstate for a prior first signal with the current count state of saidcounter to provide a second signal in response to identity in the countstates compared; means for counting sequential second signals coincidentwith said first signal toward a predetermined total count; means forreinitiating the counting of said counting means prior to itspredetermined total count in response to one of said first and saidsecond signals without the other; and means responsive to thepredetermined total count of said counting means for providing an outputindication to indicate that the stored count state represents inputinformation.
 12. The two-way projection system of claim 11 furtherincluding: means responsive to said output indication, said secondsignal and the absence of said first signal for counting toward afurther predetermined total count; and means responsive to said furtherpredetermined total count for removing said output indication.
 13. Thetwo-way projection system of claim 11 wherein: said projection surfaceincludes translucent portions for forming an image and transparentportions; said projection means includes a random access projector fortransparencies containing said repertories and means for selecting atransparency for projection; said forming means including a lens; andsaid array is a generally rectangular arrangement of detectors.
 14. Thetwo-way projection system of claim 11 wherein: said forming meansincludes a mask having a pattern of angled light transmissive slits; andsaid detector array includes a single row of detectors and a singlecolumn of detectors.